While working an a BC-221 frequency meter project, I came across a simple buffer amplifier circuit using two 2N2222A bipolar transistors.   I simulated it just to check it out, but decided it is an excellent tutorial example.  

A two-stage example is educational in that it raises the question  of which stage is limiting the output power, the first or the second.  Plotting the transistor operating path (collector current versus collector voltage) reveals what will limit output power, either current clipping, voltage clipping, or ideally, symmetrical voltage and current clipping.

The circuit is from web pages by Greg Latta, AA8V, here and by  Douglas Pongrance, N3ZI, here .  The configuration is a common-emitter stage driving an emitter-follower stage, with feedback affecting both RF gain and DC bias.

There are just a few components, and the 2N2222 is so common, there is no time consumed searching for a device model or a purchasing  source.  It just begs for experimentation of one kind or another.